Drugs sildenafil

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESTMS) for analysis of sildenafil has also been developed and applied to 40 botanical products. About half of the analyzed samples proved to contain undeclared additives of the three drugs sildenafil, vardenafil, and tadalafil <2004JPBA525>. A similar electrokinetic capillary chromatography method to that proposed for the determination of sildenafil 82 has been reported for vardenafil 98 and tadalafile 99. Statistical evaluation of the electrophoretic results was achieved. The described method is thought to be rapid and sensitive <2004JCH231>. 

Viga tablets Best of Life International 05/29/2003 Contains unlabeled drug sildenafil... 

Panke et al. (2003) also demonstrated enhanced reaction control, with respect to the temperature-sensitive synthesis of 2-methyl-4-nitro-5-propyl-2H-pyrazole-3-carboxylic acid 219, a key intermediate in the synthesis of the lifestyle drug Sildenafil (220) (Scheme 64). When performing the nitration of 2-methyl-5-propyl-2H-pyrazole-3-carboxylic acid 219 under adiabatic conditions, with a dilution of 6.01kg 1), Dale et al. (2000) observed a temperature rise of 42 °C (from 50 to 92 °C) upon addition of the nitrating solution. As Scheme 63 illustrates, this proved problematic as at 100 °C decomposition of the product 219 was observed and in order to reduce thermal decomposition of pyrazole 219, and increase process safety, the authors investigated addition of the nitrating solution in three aliquots, which resulted in a reduced reaction temperature of 71 °C and an increase in chemoselectivity unfortunately, the reaction time was increased from 8 to 10 h. 

Other useful enzyme inhibitors include acetazolamide (Diamox) (carboific anhydrase inhibitor) for the treatment of glaucoma, congestive heart failure, epilepsy and motion sickness (a very useful drug ). Sildenafil (Viagra), famous for treatment of impotence, inhibits a phosphodiesterase enzyme (PDE5) that is involved in the breakdown of ATP. 

The drug sildenafil, sold imder the trade name Viagra, is a potent inhibitor of phosphodiesterase V (PDE V), an enzyme found in high levels in the corpus cavemosum of the penis. Inhibitors of this enzyme enhance vascular smooth muscle relaxation and are used for treatment of male impotence. Following is an outline for a s)mthesis of sUdenafil. 

Reduction of Chemoselective Reaction Time Panke et al. demonstrated enhanced reaction control in the crucial step of nitration of the pharmaceutically relevant intermediate l-methyl-3-propyl-li/-pyrazole-5-carboxylic acid, a precursor to the lifestyle drug sildenafil citrate (Viagra) [5]. Control of the reaction temperature is absolutely necessary because the decay of the product above 100 C creates excess CO2 pressure and heat buildup. A standard 70 mL CYTOS microreactor was fed with reagents using external pumps. A flow rate of 1 mL/min was maintained within each channel, with the reaction temperature maintained at 90 °C. 

Erectile dysfunction is treated by local or systemic application of vasodilator drugs. The most effective is sildenafil, a phosphodiesterase-type 5 inhibitor. 

Currently, one of the most well-known, promising therapeutic drugs in relation to endogenous NO is sildenafil. The main phosphodiesterase in the human... 

Dear M. Sildenafil for hypertension Old drug, new use. Drug Topics 2005 Jul 11, http //www.drugtopics.com/drugtopics/article/articleDetail.jsp id=169471... 

The most dramatic difference between the three agents is tadalahl s extended duration of action, earning it the nickname the weekender drug. While sildenafil and vardenafil have average half-lives of 3 to 4 hours, tadalafil s half life is approximately 18 hours.18 The extended half-life allows for more spontaneous sexual activity over a couple of days, but may increase the duration of adverse effects and liklihood of drug interactions or sildenafil. 

Erectile dysfunction The addition of sildenafil or an other erectogenic drug may be helpful... 

A drug-drug interaction is possible with sildenafil and which of the following agents ... 

Unless otherwise stated, general information applies to the entire class of phosphodiesterase inhibitors. Sildenafil is highlighted because it was the first to be marketed and is the most thoroughly studied. The newer agents tadalafil and vardenafil have different pharmacokinetic profiles (Table 83-3), drug-food interactions, and adverse effects. 

Adulteration, which can be accidental or deliberate, is another problem. Many herbal products have been found to contain prescription or OTC drugs and dangerous heavy metals. In 1998, for example, the California Department of Health reported that 32% of Asian herbal medicines sold in that state contained undeclared pharmaceuticals or heavy metals. A subsequent study of more than 500 Chinese herbal medicines found that about 10% of them contained undeclared drugs or toxic levels of metals. The FDA and other investigators have also detected sildenafil, colchicine, adrenal steroids, alprazolam, and other prescription drug ingredients in products claimed to contain only natural ingredients. 

Very often, drugs are discovered through persistent work and continual optimization and many tests and trials. This is exemplified by the history behind the discovery of sildenafil (Viagra, Pfizer), a drug for the treatment of erectile dysfunction, and the AIDS drug zidovidine (Retrovir, GlaxoSmithKline) (Exhibits 3.18 and 3.19). 

The long, tortuous path from drug discovery to commercialization is amply demonstrated by the sildenafil (Viagra) story. 

Sildenafil was developed. However, there are different types of PDEs (nine are known today). As discussed previously, a potent drug has to be specific. Sildenafil inhibits PDE-5, which is absent in the kidney, although sildenafil s effect on smooth muscle relaxation was confirmed. The direction of the drug changed to treating angina instead, as sildenafil relaxes the vascular muscle of the heart. 

Hence, we can see how the focus of treatment for sildenafil changed from antihypertensive to angina treatment to overcoming erectile dysfunction, giving rise to the drug called Viagra. 

A 58-year-old man with a history of angina for which he occasionally takes isosorbide dinitrate is having erectile dysfunction. He confides in a colleague who suggests that sildenafil might help and gives him three tablets from his own prescription. The potentially lethal combination of these drugs relates to... 

A further characteristic of this principle is that, if the activity of phosphodiesterase is decreased, the concentration of cyclic GMP will increase to an extent dependent upon the extent of the decrease in activity. This characteristic has been made use of by the pharmaceutical industry. Cyclic GMP has a vasodilatory effect and this is the case for the arterioles that supply blood to the corpus cavemosum in the penis, which controls the erection of the penis. Drugs were developed (e.g. sildenafil) that inhibits cyclic GMP phosphodiesterase and hence increases the cyclic GMP level which resnlts in vasodilation of the arterioles and an increase in the snpply of blood to the spongy tissue of the corpus cavemosum, which expands resulting in erection. This dmg has been found to be effective in some patients snffering from erectile dysfunction. This can be a particular problem in diabetic patients and more elderly men (Chapter 19). 

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